The invention relates to a laser diode arrangement having a heat sink with channels for liquid coolant.
To achieve great laser power using low-cost components, so-called “laser bars” are manufactured using wafer technology. Such bars are formed by strip-shaped chips that comprise several individual emitters adjacent to each other. The individual emitters are electrically connected in parallel. Usually, the strip-shaped chip is mounted on a heat sink.
A laser bar may contain approx. 50 individual emitters, each of them emitting one laser beam that exhibits a beam angle of approx. 40° in one direction (fast axis) and of approx. 12° in the other direction (slow axis). Using collimation lenses, the individual beams are combined and parallelized.
To achieve even greater laser power, such bars are arranged to form so-called “stacks”. Depending on the application, both horizontal and vertical stacks have been known. Typically, the individual laser bars are electrically switched in series in these stacks. Such stacks are capable of generating an optical power of approx. 1 kW. Due to the high packing and power density, the individual bars are in turn mounted on heat sinks. To achieve a high service life of the expensive laser bars, the heat sinks are cooled by a coolant, avoiding overheating of the laser bars.
In known laser diode arrangements, a coolant channel that runs along the longitudinal axis of the laser bar is provided below the heat sink. This ensures good cooling in the area where the coolant enters the coolant channel. While passing through the cooling channel, the coolant heats up more and more, such that in the area where coolant exits from the coolant channel, only a small amount of heat can be withdrawn from the heat sink. Thus, the laser bar can overheat locally in this area.
EP-A-O 973 237 discloses a semiconductor laser arrangement with a mounting plate that has a feed channel and discharge channel worked into it. A separate heat sink is provided for each laser diode array which is mounted on the mounting plate. The feed channel and discharge channels are connected to each other via cooling channels that run through each individual heat sink.
JP 2004 193228 A discloses a laser diode arrangement that is mounted on a heat sink. A feed channel and discharge channel for coolant as well as cooling channels that connect the feed to the discharge channel and run close to the laser diodes are provided in the heat sink.
The laser diode arrangement according to EP-A-1 450 454 is designed in a similar manner to the arrangement according to EP-A-O 973 237. Here too a plate is provided with a feed channel and a discharge channel for the coolant worked into it. Likewise, a separate heat sink is provided for each laser diode array and is mounted on the mounting plate. In the same manner, the feed channel and discharge channel are connected to each other via cooling channels that run through each individual heat sink.